The present invention relates to a side airbag apparatus that protects an occupant from impact applied from a side of a vehicle, and in particular, the present invention pertains to a side airbag apparatus in which the airbag is provided with chambers that are inflated with different internal pressure levels.
A side airbag apparatus is widely known as an apparatus for protecting an occupant from impact applied from a side of a vehicle, such as in the case of side collision. The side airbag apparatus includes an inflator and an airbag. In the side airbag apparatus, when an impact is applied from the side of a body side portion of a vehicle, the inflator discharges gas into the airbag. The discharged gas causes the airbag to shoot forward from the seat back, which is then inflated and deployed in a narrow space between an occupant seated in the vehicle seat and the body side portion so as to reduce the impact applied to the occupant from the side via the body side portion.
In general, in regard to the side portion of a human body, the lumbar region has higher impact resistance than the chest region. Thus, in the case with the side airbag apparatus that protects an area from the chest region to the lumbar region of the occupant, the impact applied to the chest region of the occupant by the inflation and deployment of the airbag is desirably smaller than the impact applied to the lumbar region.
Thus, a side airbag apparatus has been proposed in which the internal space of the airbag is divided into an upper chamber corresponding to the chest region of the occupant and a lower chamber corresponding to the lumbar region. For example, in a side airbag apparatus disclosed in Japanese Laid-Open Patent Publication No. 2004-210048, the airbag is provided with a coupling portion, which couples an upper chamber and a lower chamber. An inflator having two outlets is arranged at the coupling portion. Part of the airbag corresponding to the coupling portion is tightened to the inflator by a tightening member such as a hose band. In the side airbag apparatus, in response to an impact from the side of the vehicle, gas is discharged to the upper chamber from an upper outlet of the inflator, and gas is discharged to the lower chamber from a lower outlet by an amount greater than that discharged to the upper chamber. As a result, part of the airbag corresponding to the lower chamber is inflated and deployed beside the lumbar region with high internal pressure, and part of the airbag corresponding to the upper chamber is inflated and deployed beside the chest region with low internal pressure. Thus, the airbag is brought into contact with the occupant with the internal pressure appropriate to the impact resistance of each region of the occupant so as to effectively protect each region of the occupant from the impact. Since the upper chamber and the lower chamber are hermetically separated by the tightening member, gas does not flow between the chambers, and the internal pressure difference of the chambers is maintained.
Also, a side airbag apparatus has been proposed in which an inflator having one outlet is arranged in a communication portion. In such a side airbag apparatus, when gas is discharged from the outlet of the inflator in response to the impact from the side of the vehicle, gas is first supplied to the lower chamber, and then flows into the upper chamber through the communication portion. Since the gas flows in this order, the lower chamber is inflated and deployed in preference to the upper chamber, and is inflated and deployed with the internal pressure higher than that of the upper chamber. That is, in this side airbag apparatus also, the difference between the impact resistance between regions of the occupant is taken into consideration for the pressure distribution in the airbag.
However, according to the side airbag apparatus disclosed in Japanese Laid-Open Patent Publication No. 2004-210048, the coupling portion merely functions as a position for arranging the inflator. Part of the airbag corresponding to the coupling portion is brought into close contact with the inflator by the tightening member. That is, the coupling portion is closed, and the flow of gas at the coupling portion is always blocked. Thus, the flow of gas at the coupling portion cannot be controlled, and the internal pressure difference between the upper and lower chambers is determined by the amount of gas discharged from the outlets of the inflator.
Furthermore, according to the latter side airbag apparatus, the communication portion functions as a position for arranging the inflator, and also as a passage for allowing the gas to flow from the lower chamber to the upper chamber. However, in this side airbag apparatus, the area of the passage in the communication portion is uniform, and the communication portion does not control the flow of gas. Thus, in this case also, the internal pressure difference between the upper and lower chambers is determined by the discharged amount of gas from the outlet, the area of the passage in the communication portion, and the like.